dart - Flutter 如何在 List 映射中映射一个完成的 Future 对象

Question

Future<List<Future<News>>> getNewsList(skipItems) async {
    final response = await http.get(
        'https://hacker-news.firebaseio.com/v0/topstories.json?print=pretty');

    if (response.statusCode == 200) {
      // If the call to the server was successful, parse the JSON
      var responseNewsList = json.decode(response.body);
      newsList = responseNewsList as List;
      var resNewsList = (responseNewsList as List)
          .skip(skipItems)
          .take(20)
          .map((id) =>  this.fetchNewsDetails(id))
          .toList();

      return resNewsList;
    } else {
      // If that call was not successful, throw an error.
      throw Exception('Failed to load post');
    }
}

Future<News> fetchNewsDetails(id) async {
    final response = await http.get(
        'https://hacker-news.firebaseio.com/v0/item/$id.json?print=pretty');

    if (response.statusCode == 200) {
      // If the call to the server was successful, parse the JSON
      return News.fromJson(json.decode(response.body));
    } else {
      // If that call was not successful, throw an error.
      throw Exception('Failed to load post');
    }
}

因此您可以在代码中看到我尝试获取热门新闻帖子的列表，但响应只返回一个 ID 列表，因此我需要调用另一个 API 来获取帖子的详细信息，就像上面我说的那样将需要使用两次 Future Builder 来显示内容，这种方式可行，但我是否可以等待响应返回并将发布结果放入映射函数？

Answer 1

我假设你想要

await Stream.fromIterable((responseNewsList as List)
      .skip(skipItems)
      .take(20))
      .asyncMap((id) =>  this.fetchNewsDetails(id))
      .toList();

https://api.dartlang.org/stable/2.1.0/dart-async/Stream/asyncMap.html